Railroad car track loading system



April 25, 1967 T. J, DOSCH ETAL 3,316,400

RAILROAD CAR TR ACK LOADING SYSTEM Filed April 10, 1961 2 Sheets-Sheet 1 /a /Z1 7' f// I U H 3 g DETECTOR 1 TI 5 f /7 64B SPACE E mm, 35;;

-r 22 came/W02 I 3 cazezcrla/v commmroe DEV/CE 77 2 CA2 space MEMOEV 051005 C42 cod/Y7 7-0 (004F075? A 1 25.567 600266 .IN VEN TORSI THOMAS J. BOSCH WILLIAM V. FLUSH/[VG AGE/VT A rii 25, 1967 T. J. DOSCH ETAL RAILROAD CAR TRACK LOADING SYSTEM 2 Sheets-Sheet 2 Filed April 10,

United States Patent 3,316,40t) RAILROAD CAR TRACK LOADING SYSTEM Thomas J. Bosch, Huntington, and William V. Flushing, tony Brook, N.Y assignors, by mesne assignments, to Dynamics Corporation of America, New York, N.Y., a corporation of New York 1 Filed Apr. 10, 1961, Ser. No. 102,046 26 (Ilaims. (Cl. 246-182) The present invention relates to a system for determining how many empty car spaces are available upon a storage track in a railroad car classification yard.

In modern railroad classification yards an automatic speed control system operates a group retarder for braking railroad cars. Each car leaves the retarder at a computed exit velocity to reach its destination along a storage track at a desired speed for coupling with a previous car. The distance a car must go to its intended coupling point from the group retarder is one of many variable factors that must be known for computing the exit velocity.

In previous speed control systems, the number of empty car spaces along each storage track has been retained by a memory-device. This number is used for determining the distance-to-go from the group retarder to the last car on the storage track. Each time a car leaves the group retarder, the number retained by the memory device associated with the track to which the car is to go is automatically decreased by one car.

As a storage track is filled the information retained by its memory device may not accurately represent the number of car spaces that actually are available. This can occur because all cars do not occupy spaces of equal lengths nor do they all reach their intended destination.

From time to time the human operator of the system might estimate the number of empty car spaces actually left upon the storage track and apply a correction to the memory device. However, human error, weather conditions or other factors often cause the correction to be inaccurate. The end result is that a car sometimes leaves the group retarder at the Wrong speed and either stops short of its destination or couples too hard with a previous car upon the storage track.

The necessary correction to the memory device might be made automatically by making its output correspond with a signal generated in accordance with the distance between the input end of a storage track and the last car on the track. This signal is useful only if the last car on the storage track is not rolling.

It is an object of the present invention to provide improved means for automatically determining the distance a movable object must go along a path to reach a previous object further along said path, despite the fact that the previous object sometimes may be moving at the time the distance-to-go is determined. 7

It is a further object to provide improved means for automatically generating and storing information related to the number of empty car spaces left on a storage track in a railroad classification yard.

It is another object to provide means for producing accurate information related to the number of empty car spaces available or expected to be available along a storage track in a railroad classification yard, regardless of Whether or not a previous car is moving along the storage track.

It is still another object to provide a track loading system for storing railroad cars wherein all of the cars can be removed from a storage track at any time during a car classification operation without affecting the accuracy of the information provided about the number of car spaces left along that track.

The foregoing and other objects and advantages of the ice invention are attained by providing a memory device for storing informationrelated to the number of car spaces along each storage track, means for decreasing the output of the memory device by a predetermined amount for each car that enters the retarder for that track, and means for automatically correcting the output of the memory device from time to time in accordance with the empty car spaces actually available along the storage track. The correcting means comprises means for producing and storing information related to the actual number of empty car spaces along the storage track, a comparator for producing an output if there is a difference between the actual number of emptycar spaces and the number of empty car spaces stored'by the memory device, and means for correcting the output of the memory device to reduce .any difference. A moving car detector is provided for interrupting the operation of the correcting means if a car is moving along the storage track during an interval that the correcting means otherwise would be operable for correcting the memory device.

In the accompanying drawings,

FIGURE 1 is a schematic plan view of part of a railroad classification yard;

FIGURE 2 is a simplified block diagram of the system of the present invention; and

FIGURE 3 is a detailed schematic diagram of a preferred embodiment of the invention.

Referring to FIGURE 1, the numerals 1-8 refer to a group of storage tracks for railroad cars in a gravity railroad classification yard. There are "n" ca-r spaces between the clearance point at the entrance of each storage track and the end of a track. Each car space is equal to the average length of a railroad car, i.e., feet, for example. A typical storage track has room for 60 cars of average-length.

The storage tracks 1-8 are connected to a branch track 11 by short sections of track and suitable track switches; not shown. These switches are operated automatically by means known in the art for directing each car to a predetermined storage track. The branch track 11 is connected by a suitable track switch, not shown, to a main track 12 upon which a car is received from the hump and a master retarder, neither of which are shown, along main track 12. The branch track 11 includes an acceleration measuring section 13 for determining the acceleration of each car as it approaches a group retarder track section 15. Car acceleration, together with information related to the char acteristics of the track between the'retarder section 15 and the destinationupon a storage track for each car, are used'for computing the exit velocity at which a car must leave the group retarder section to reach its destination with a desired coupling velocity.

Means for computing the exit velocity from the above information and for operating the group retarder along section 15 are well known in the art. One suitable arrangement is shown and described in US. application Ser. No. 476,278, filed Dec. 20, 1954 by Perry A. Seay and assigned to the same assignee as the present invention. 1 Y In a typical classification yard other branch tracks 11 and 11", each terminated by a group of storage tracks; not shown, are also provided. Each of branch tracks 11 and 11" includes an acceleration measuring section and a group retarder section similar to those along branch track 11. Instead of providing an acceleration measuring section upon each of the branch tracks 11, 11', and 11" as described .above, it is apparent that one acceleration measuring section only might be provided along the main track 12 for determining a cars acceleration before it enters a branch track, if preferred.

. .3 The distance a car must roll from a fixed point at theexit end of the group retarder to a car coupling point at a destination along a particular storage track is one of the trackcharacteristics that must be known before the group retarder exit velocity for a car can be computed accurately. In previous systems the distances to roll for the various cars for each storage track are determined by a-memory device that retains the number of-empty car spaces available along a storage track. Because of the difficulty in supplying accurate corrections to the memory device, previous systems are not entirely satisfactory.

1 Referring to-FIGURE 2, a system in accordance with the present invention is shown for determining and storing the number of empty car spaces that areavailable along any one of the storage tracks 1-8 shown in FIG. l during a classificationoperation, and for automatically correcting this number. The "ming sequence of a timer 18 is initiated by acar as-it approaches the acceleration measuring section 13. Five discrete outputs are produced by, timer 18 at progressively increasing moments T T T T and T afterthe timing sequence is initiated. The output at T recycles the-timer 1 1 A car space information generator-16 produces information related to the actual number of empty car spaces available along a particular storage track at any moment. Storage device 17 remembers the output produced by generator- 16 v Signals -aresupplied to device 17 from timer 18 to' make device 17 respond to the output of generator 16 only during a-time intervalT -T 1 Car space memory device 19 has two outputs that can be set .tocorrespond with the output of device-17.- One of the outputs of memory device 19 issupplied to a computer, not shown,- for-determining thedistance a car must go from agroup retarder to the last-car on the storage track associated with device 19. The other output of device 19Iis supplied to a comparator 22. v The comparator22, uponreceiving a signal fromtimer 18 at a moment T produces an output it there is a difference between the output of the storage device 17' and the output of the memory device 19." The output of comparator 22 operatesa correction device 21,whose output is suppliedto thecar space memory device 19 for making the outputs of devices 17 and 19 equal.-

Moving car detector 23 responds to changes in the output ofthe-information generator- 16 forinterrupting the operation ofcorrection device 21 if-a caris moving upon the storage track. Signals are supplied to detector 23 fromtimer 18 for making the detector responsive to the output of generator 16 only during an interval T T Gar :count reset-sourcedecreases the output of the space memory device 19 byhnity, for example, each time a signal is received from timer 18 at a moment T At a moment T the timer 18 recycles itself.

. Inoperation. of the system shown in FIGURE 2, referencealso is made to the diagram shown in FIGURE 1. Assume that the carspace information generator 16 and the car. space memory device 19 are associated with the storage track 1, and that the track switches are properly set for making a car go to track 1. Before the car enters the acceleration measuring section 13, it initiates the sequence of timer 18.

During the intervaLT -T- the storage device 17 re sponds to the output of the information generator 16 for memorizing the number of car spaces actually available along 'the storage track.

i 1 At the moment T another output from'the timer 18 conditions the comparator device 22 foroperation. If the outputs of device 19 represent anumber that is. different from the number represented by the output of device 17,a signal is supplied to thecorrection device 21 by comparator 22. If no car is moving on the storage track 1,, the correction device 21 operates to make the outputs of the carspace memory device 19 correspond with the output of device 17. If a car is moving'a'long storage 4 track 1 during the interval T T the moving car detector responds to the output of generator 16 and interrupts the operation of correction device 21 for the remaining portion of the sequence of timer 18. Under these conditions, the outputs from the car space memory device 19 cannot be changedby the correction device 21.

Once the car space memory device 19 has had an opportunity to be reset, and prior to T the computer, not shown, determines the distance that the car initiating the timing sequence must go to reach its intended destination. At T just before the car leaves the acceleration measuring section 13 and after its exit velocity from the retarder section has been computed for controlling the retarder by means, not shown, the car count reset source 20 operates to decrease by unity, for example, the number of car spaces indicated by the memory device 19. At T the timer 18 recycles itself and the system is ready for the next car. 1 v I If-a previous car were moving along its storage track during T -T in a timing sequence for a subsequent car, it can be assumed that the previous car will reach its destination, or'come close to it. For the subsequent car, therefore, the output of the memory device 19 is substan tially correct because it Was decreased by unit-y at the moment T during the timing sequence for the previous car. Thus, the device 19 indicates the number of empty car spaces that are expected to be available for the subsequent car, and the information supplied to the computer is substantially correct for determining the distance-to-go forv the subsequentcar.

A more detailed showing of the system illustrated in FIGURES. l and 2 isshown in FIGURE 3. Only the branchtrack 11 and the .storage'track 1 areillustrated. Both the number 1 and the number 2 rails of the branch and storage tracks are shown. The ends of the two rails of track 1 are short circuited by a connection 29. I 1 Each of the relays shownuin the dotted line block 18 in FIG. 3 has a coil and at least one armature for making and breaking a connectionbetweena fixed contact and a movable contact carried by the armature. Each coil is designated by two capital letters. An armature controlled bya particular coil is referred to by the same set of letters as the coil and a numericalsubscript. These armatures are distributed through the system shown by FIG. 3. I In FIGURE 3, the relay armaturesare shown in positions when their respective relay coils are de-energized, i.e'., not conducting current. Each relay is of the break before make type. If a relay has two or more armatures and tWo or more sets of contacts, a closed set opens just before an open set closes.

TIMER 18 The timer consists of a source 30 of D.C. operating potential, at switch 31, a current limiting resistor 32, and a group of relays having coils KA, KB, KC, KD, KE, KF. Three relay armatures KA KA and KR are controlled by the similarly lettered relay coils. The relays KB, KC, KD, and are time delay relays. The respective armatures associated with the time delay relays are actuated at progressively increasing moments T T T T and T after these relays are energized. These moments occur 3 sec., 3.1 sec., 10 see, 12 sec.,and 12.5 sec., respectively, after the coils KBKF are energized, for example.

The armature KA is provided for connecting one terminal of each of the relay coils KB, KC, KD and KP to the power source 30. The other terminals of these coils are connected to ground. One terminal of the KA relaycoil is connected to ground, its other terminal being connected to the power source 30 by current limiting resistor 32.v

The other terminal of relay coil KA also is connected to a terminal 33 on rail #2 of the branch track 11. Terininal 33 is ahead of the accelerationmeasuring section 13 by a distance which is sufiicientjto permit the timer 18 to proceed through its timing sequence before the cal? SBIBAOO that initiates the sequence arrives at section 15. The terminal 33 is insulated from rail #2 by non-conductive members 34 and 35. Rail #1 of branch track 11 is grounded as illustrated in FIG. 3.

In operation of the timer 18, when the switch 31 is closed the coils KB, KC, KD, KB and KP are energized simultaneously through KA The coil KA is not energized at this moment because its terminals are short circuited by the armatures KA and KP At predetermined moments after energizing coils KB- KF, the various armatures associated therewith, which are distributed throughout the system of FIG. 3, change from the positions illustrated to their other positions. An open armature closes to make a circuit and a closed armature opens to break a circuit. At the end of a timing sequence the armature KF is actuated and the short circuit across the terminals of relay coil KA is removed. The coil KA is energized and the armatures KA and KA open, deenergizing the coils KB-KF inclusive. The armatures associated with these coils simultaneously change back to their positions shown in FIG. 3. Although the KF armature closes at the moment coils KB-KF are de-energized, no short exists across the relay coil KA because armature KA opens at the moment coil KA is energized, and remains open until a short is produced across its terminals. Thus, armatures KA and KA are open prior to receiving the first car for classification upon storage track 1.

As a received railroad car rolls down the track 11 from the master retarder, not shown, and crosses terminal 33, both terminals of coil KA are momentarily grounded, deenergizing this coil. The armatures KA and KA close, and the time delay relay coils KB-KF areenergized. initiating the timing sequence. Then, the armatures associated with the coils KB-KF are reversed from the position shown in FIG. 3 at the moments T T T T and T respectively. As has been explained above, these moments occur at progressively increasing times that are delayed from the particular moment that relay coils KB-KF are first energized at the beginning of a timing sequence. The timing sequence ends at the moment T when the armature KF is opened by the relay coil KF.

INFORMATION GENERATOR 16 The car space information generator 16 includes a power source 37 of alternating potential at 115 volts, 60 cycles per second, and a transformer 38 for stepping down this voltage to 6 volts, for example. The output of transformer 38 is supplied through series resistor 43 and leads 44 and 45 to the two rails of the short-circuited section of storage track at terminals 48 and 49. The terminal 49 is insulated from rail #2 of the branch track 11 by a non-conductive member 50. Terminals 48 and 49 are located at the track clearance point at the entrance of storage track 1.

The voltage drop across resistor 43 is supplied to the primary winding of a transformer 46, the resistance of resistor 43 being very small compared with the impedance of the primary winding of transformer 40. The voltage drop across storage track 1 at terminals 48 and 49 is supplied to the primary winding of a transformer 39. These voltage drops are equal if there are no cars along the storage track 1. The transformers 39 and 40 step up each of these voltage drops by approximately 30:1, for example.

The short-circuited track 1 simulates an inductor. This inductor is represented schematically by the dashed line configuration 51 connected in series with resistor 43. The reactive impedance of inductor 51 is related to the distance from terminals 48, 49 to the short circuited end of track 1, or to the last car on the track which short circuits the two rails of track 1. Therefore, the voltages across the primary and secondary windings of transformer 39 are proportional to the above distance.

Rectifiers 53 and 54 change the outputs of transformers 39 and 40, respectively into D.C. voltages -of opposite polarities with respect to ground. The output of rectifier 53 is a track voltage whose magnitude is related to the distance between the short circuited end of track 1 and the terminals 48, 49. The output of rectifier 54 is a reference voltage for the memory device 19.

In operation of the car space information generator 16, if no cars are on track 1, a maximum track voltage is produced at the output of rectifier 53, which is equal and of opposite polarity to the voltage at the output of rectifier 54. If a car is received on the storage track 1, it short circuits the track at a point nearer to the terminals 48, 49 than the member 29. The reactive impedance of the track is reduced, and the track voltage at the output of rectifier 53 decreases. This voltage is related to the number of empty car spaces between the terminals 48, 49 and the last car received by track 1. The track voltage increases as the car rolls down the track, and is related to the distance between the track clearance point and the last car on the track.

MOVING CAR DETECTOR 23 The moving car detector includes an operational D.C. amplifier 56 whose output is connected to a relay coil MA by an armature KD The amplifier 56 has a negative feedback circuit, including a resistor 62 and a capacitor 63 connected in parallel. The input of the amplifier 56 includes a resistor 57, armatures K13 KB and a capacitor 61. The amplifier 56 and circuit components associated therewith comprise means for differentiating and smoothing the DC. track voltage from the information generator 16. The amplifier 56 produces an output only if its input varies because of a moving car on track 1.

l 1 The armatures KB and KB keep undesired input currents from being applied to the amplifier 56 until T when KB is closed and KB is opened by the relay coil KB of timer 18. The closed contacts open before the open contacts close for preventing the input of amplifier 56 from being grounded. The armature KD is opened at T by the relay coil KB of timer 18 for disconnecting the relay coil MA from amplifier 56. The armature KD remains closed for the time interval from T -T which intervalis sufficiently long to permit relay coil MA to be energized .by the output of amplifier 56, if there is a moving car,

in spite of the delay caused by the smoothing networks. It the differentiating were achieved without smoothing, noise voltages which appear superimposed on the track voltage from rectifier 53 might produce a moving car output even though no car were moving on track 1.

The moving car detector 23 also has a source of D.C. power 66, a pair of serially connected armatures KA;; and MA and an armature MD connected across MA The KA armature is actuated by the KA relay coil of timer 18. The MA armature is actuated by the- MA relay coil of the moving car detector 23, and the MD armature is acuated by a relay coil MD in the correction device 21.

In operation of the car detector 23, if a car is moving along track 1 the magnitude of the track voltage input to detector 23 gradually changes. During the interval T T when armature KB is closed and armature KB is open, this voltage is differentiated and smoothed by detector 23 to produce an output that energizes relay coil MA through the closed armature KD closing armature MA The moving car detector should be sufiiciently sensitive to cause armature MA to close in response to a car moving at a speed as low as one mile per hour.

The closure of armature MA connects the DC. power source 66 to the relay coil MD in the correction device 21, provided armature KA also is closed. The armature KA is closed as long as the relay KA of timer 18 is de-energized, which occurs from the beginning of the operating sequence of timer 18 until T When the relay coil MD of the correction device 21 is energized, the armature MD of the moving car detector l timer 18'. The amplifier 71 amplifier 81.

7 closes. This keeps the coil MD connected to the power source 66 throughout the remaining portion of the full operating sequence of timer 18 until T despite the fact that the KD armature opens at T or the fact that a moving car might stop immediately after T If no car is moving on track 1 during the interval "f -T the armature MA remains open and the relay coil MD cannot be energized. 'ment relay coil KA is energized again. Thus, relay coil MD is always de-energized at the end of each timing sequence'.

STORAGE DEVICE 17 The storage device 17 consists of an operational D.-C. amplifier 7-1 and a capacitor 72 for storing a voltage related to the magnitude of the track voltage output of the information generator 16. One terminal of capacitor 72 either'is grounded by an armature KC or is connected back to the input of amplifier 71 by an armature KCg. The input to amplifier 71 is connected to the track voltage output of the information generator '16 by armatures KB KC and resistor 73.

The amplifier 71 has a negative feedback circuit ineluding a resistor 76 in series with a pair of armatures KC; and KB An armature K3 and a stabilizing capacitor 77 are connected in parallel between the input and output of the amplifier. 1

In operation of the storage device 17, the D-.-C. track voltage produced by the information generator :16 is applied to amplifier 71 at the moment T that the armature KB is closed by relay coil KB of timer 18. The armature KB also closes and the armature KB opens. Capacitor 72 is charged to a voltage related to the magnitude and polarity of the voltage produced by track voltage rectifier 53.

At the moment T are opened and KC the armatures KC KC and K is closed by the relay coil KC of is disconnected from the information generator v16 and the capacitor 72 is connected back to the input of the amplifier 71. The capacitor 77 prevents any change in voltage across capacitor 72 during the brief interval between the opening of armature KC and the closing of armature KC The armature KC opens before armature KC closes to prevent the input of the amplifier 71 from being connected directly to ground. The voltage across capacitor 72 is applied to the'comparator 22.

.THE CAR SPACE MEMORY DEVICE 19 This device consists of an operational D.-C. amplifier 81, a capacitor 82, and a stepping switch generally referred to by numeral 8-3. The input to the amplifier 81 is connected to the reference voltage output of the infor mation generator 16 by armature K13 armature KC and resistor 86. The amplifier 8.1 has a negative '-feedback circuit consisting of a resistor 84 and a pair of armatures KC and K13 in series. The armature K3,; is connected to a movable tap on a potentiometer resistor 87 for adjusting the gain of amplifier 81.

An armature KBq and a stabilizing capacitor 88 are connected in parallel between the output and input of An armature ICC- is provided for connecting the capacitor 82 back to the input of the amplitier. An armature switch K0 is provided for connecting the capacitor 82 to ground.'

A resistor -89 of the stepping switch '83 is connected between ground and one terminal of capacitor 82 at the output of amplifier 81. The contacts of a semi-circular bank of contacts are connected to different points along resistor 89, each contact representing a different number of car spaces. There is one contact for each car space upon storage track 1 between the track clearance point and the short circuit 29 at the end of the track. An arm 90 of the stepping switch is movable from contact to contact for supplying the comparator 22 with a current that The armature KA opens at T at the mo- 83 is energized by cluding a pair of resistors 55 is related to the position of arm and the magnitude of the voltage stored by capacitor 82. The arm 90 is rotatable in a clockwise direction, for example, and has diametrically opposite terminals for engaging the contacts of resistor 89. These contacts are arranged so that arm 90 engages only one contact at a time along the resistor 89 as the arm 90 is rotated.

The rotatable arm 90 of the stepping switch is coupled to a computer, not shown, for supplying the computer with information relating to the position of arm '90 and the number of car spaces indicated by the memory device 19. Although FIG. 3 indicates that mechanical information is supplied to the computer, itis readily apparent that electrical information might be supplied instead.

With no cars on storage track 1 and the arm 90 in an empty track position, the direct currents supplied to comparator 22 by memory devices 17 and .19 are substantially equal in magnitude and opposite in direction. This can be assured by adjusting the tap on potentiometer 87 to vary the gain of amplifier 81.

A solenoid coil 91 comprises part of the stepping switch 83 for actuating the stepping switch arm 90. One end of coil 91 is connected to ground, its other end being connected to the correction device 21 by an interrupter 92. This other end also is connected to the car count reset source 20.

If correction device 21 produces an output, it energizes solenoid coil 91 through the interrupter 92. The magnetic field of coil 91 actuates the interrupter for operating a ratchet wheel, not shown, which rotates the switch arm 90 by one step in a clockwise direction. The circuit between coil 91 and the correction devices 21 is broken as soon as the interrupter is actuated. Thus, after causing the switch arm 90 to be rotated by one step in one direction only, the interrupte r'ag-ain returns to its original position, arm 90 remaining at its last position. At the momentthe interrupter 92 completes the connection between coil 91 and the correction device 21, the interrupter 92 is actuated again, assuming that an output still is provided by the correction device 21. Thus, theswitcharm 90 is moved in steps from one to the next adjacent contact connected to resistor 89 as long as an output is produced by the correction source 21.

At the moment T, when the coil 91 of stepping switch an output from the car count .rese-t source 20, the arm 90 is rotated one step by the interrupter 92. Since the interrupter is not in series with the reset source 20 and coil 21, the coil 91 remains energized as long as an output is produced by source 20. Iherefore, the interrupter 92 remains at its energized position to rotate arm 90 by one step only.

COMPARATOR DEVICE 22 The comparator device 22 consists of an operational D.-C. amplifier 93 having an input summing network in- 94 and 95 connected to the outputs of the memory devices 17 and 19, respectively. A capacitor 96 and a resistor 97, whose resistance value is relatively low compared to the resistance value of resistor 95, is connected across resistor 95.

A potentiometer 93 connects the output of amplifier 93 to ground. A resistor 99 is connected between a movable tap upon resistor 98 and the input of amplifier 93 for providing a negative feedback path. The gain of amplifier 93 is regulated by the position of the movable tap upon the resistor 98.

In operation of the comparator device 22, if the output currents of devices 17 and 19 are equal and opposite, the sum of the currents at the summing junction of amplifier 93 is substantially zero. Thus, the output of amplifier 93 is substantially zero or at a minimum value. If the currents supplied to the input of amplifier 93 are unequal, an output is produced which is supplied to the correction s0urce'21 through an armature switch KD when this armature is closed. It is closed from T to T by the relay coil KD of the timer '18. If the armature MD of the correction device 21 also is closed and the output of amplifier 93 is above a predetermined minimum value, the TL relay coil of device 21 closes the TL armature. At this moment an output is produced by the correction device 21.

CORRECTION DEVICE 211 The correction device comprises a DC. power source 101, the relay coil TL, the armature TL a relay coil MD and the armature MD The output of device 101 is connected to the energizing coil 91 of the stepping switch 83 through the interrupter 92 for operating the switch arm 90 during the interval that armature IL is closed. The MD relay is energized by the output of the moving car detector 23 for opening the MD armature, thereby interrupting the connection between the output of comparator 22 and the relay coil TL of the correction device 21. This prevents any output from device 21 even though an output is produced by amplifier 93 of the comparator 22.

CAR- COUNT RESET SOURCE so The car count reset source comprises a D.-C. power source 101', which might be the source 101 of the correction device 21. in also includes a relay armature KE for connecting the source 101 to the end of the solenoid 91 of the stepping switch farthest from ground. Normally, the armature KE is open. It is closed at T by the relay coil KB of the timer 18, whereby the solenoid 91 is energized to rotate stepping switch arm 91 in one direc tion only to its next adjacent-contact. Thus, the number stored by memory device v19 is reduced by one each time armature KE is closed. At T the end of the timing sequence of timer 18, the armature KE opens again, the stepping switch arm 90 remaining in the position it assumed after a previous closure of armature'KE The switch arm 90 is operated by the car count reset 20 source, preferably immediately after the retarder exit velocity has been computed for the car which initiated the timing sequence. Thus, when the next car is received the outputs of the memory device 19 are equal to the number of empty spaces that would be available along the storage track if the previous car had reached its intended destination.

OVERALL OPERATION OF SYSTEM The system is ready to determine the number of empty car spaces along storage track 1 after the switch 31 of timer 18 is closed by the operator and the timer has operated through one sequence. At the end of this first sequence, the KA relay coil is energized, the KA and the KA armature of the timer are open, and the KA armature of the moving car detector 23 is open. Since the KA armature is open, none of the relay coils KB-KF are energized, and the armatures KB K0 KE and KF are in the positions illustrated in FIG. 3.

As a car for storage on track 1 passes over terminal 33 on the branch track 11, it short circuits the terminals of the KA relay coil and this relay is de-energized. The KA KA and KA armatures, which were open, close and the relay coils KB-KF are energized. Closure of the KA armature keeps the relay coil KA short circuited because the KF armature is closed.

At a moment T shortly after the KB coil is energized, the KB armatures move from their positions shown in FIG. 3 to their other positions. The capacitors 72 and 82 of the storage device 17 and the car space memory device 19, respectively, are charged to voltages proportional to the track voltage and the reference voltage, respectively.

At a moment T which is delayed from T just long enough to permit capacitors 72 and 82 to be charged to the track and reference voltages, respectively, the KC switches change from their positions illustrated in FIG. 3 to their other positions. This disconnects the inputs of the amplifiers 71 and 81 from the outputs of the information generator 16. Also, the capacitors 72 and 82 become part of the negative feedback circuits of amplifiers 71 and 81, respect.ively.- The track voltage and the reference voltage are memorized by capacitors 72 and 82, respectively.

At the moment T the armature KD of the comparator 22 closes. The relay coil TL of the correction device 21 is connected to the output of amplifier 93, provided no car has moved along the storage track 1 during the interval T T which would have opened the armature MD If the outputs of the memory devices 17 and 19 are unequal, the TL armature closes to connect the DC. power source 101 to the stepping switch actuating coil 91. Upon energizing coil 91, the switch arm rotates until the outputs of the memory devices 17 and 19 are approximately equal and opposite, whereby the input to amplifier 93 is substantially zero. This releases the TL relay, the armature TL opens, and the stepping switch coil 91 is de-energized.

If a car is moving along track 1 during the interval T T while armature KD of the moving car detector 23 still is closed, the output from amplifier 56 energizes the MA relay coil, and the MD coil of correction source 21 is energized. This opens armature MD, to break the connection between the comparator 22 and the relay coil TL.

At a time T just before a car leaves the acceleration measuring section of track 11, the car count source 20 energizes coil 91 of the stepping switch 83. Switch arm 90 is rotated by one contact to decrease by one the car space information at the outputs of the memory device 19. At T the timer is recycled and ready for the next car.

In an actual system there is a stepping switch 83 for each of the classification tracks 18. The other equipment, however, can be common to all or many classification tracks. Suitable switching of the associated apparatus will be clear to anyone skilled in the art, it it is recalled that codes corresponding to the destination of each car are generated in an automatic hump classification yard, and that such codes can control the switching of the associated apparatus.

The switching referred to above comprises means for disconnecting the leads 44 and 45 from the classification track number 1 and connecting these leads to one of the other classification tracks 28. It also comprises means for disconnecting the output lead of amplifier 81, the computer input, and the stepping switch input lead of amplifier 93 from the stepping switch 83, and connecting them to a different stepping switch for one of the other classification tracks 2-8. Also, switching means would be provided for connecting the output leads from the car count reset source 20 and the correction device 21 to the interrupter of the foregoing different stepping switch for one of the other classification tracks.

In the system shown in FIG. 3, the moving car detector 23 and the comparator 22 include the amplifiers 56 and 93, respectively. If desired, one amplifier only could be used, provided suitable switching is employed. If this were done, switches would be used for selectively connecting the input of the one amplifier either to the output end of resistor 57 of the moving car detector or to the output end of resistors 94, 95 and 97 of the comparator. Also, switches would be used to selectively connect one or the other of the feedback circuits of amplifiers 56 and 93 across the one amplifier. These switches would be operated by relays at suitable times so that the one amplifier would function either as part of the moving car detector circuit or as part of the comparator circuit. The armature KD and relay coil MA of the moving car detector 23 would be connected to the output of the one amplifier in parallel with the armature KD armature MD;

mation related to the number track section, comprising a for resetting said device number of car spaces prior track section for charging said capacitor 1 1 and the relay coil TL of the comparator 22 and the correction source 21.

As many changes could be made in the above construction and many different embodiments could be made Without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A system for determining the distance a vehicle must go from a fixed point along a predetermined path to a variable destination within a vehicle storage section further along said path, comprising in combination a memory device for storing information relating to the length of the unoccupied space within said storage section, means for correcting said information during a predetermined time interval as a vehicle approaches said fixed point, means for detecting motion of any vehicle within said storage section during said predetermined time interval, and means for responding to the detection of said motion for precluding correction of the information stored by said memory device during said predetermined time interval.

2. The combination defined by claim 1, further including means for resetting said memory device so that its stored information is decreased by the length of one vehicle for each vehicle that leaves said fixed point.

3. The combination of claim 2 wherein said correcting means comprises means for generating information related to the actual number of storage spaces along said path, a further memory device for responding to said information during said predetermined time interval for storing inforof unoccupied vehicles storage spaces that exist during said interval, means for comparing the outputs of said memory devices during said time interval to produce an error signal, and means forresponding to said error signal for changing the information stored by said first mentioned memory device until it corresponds with that of said further memory device.

4. A system for automatically determining the distance a railroad car must roll from a group retarder track section to a car coupling point along a classification storage device for memorizing the number of car spaces left on the classification track, means for each car that leaves the retarder track section, means for correcting the memorized to the arrival of each car at the retarder track section, and means for interrupting said correcting means in the presence of a moving car upon said classification track.

5. The system of claim 4 wherein said correcting means comprises a further device for memorizing the number of car spaces actually left upon said classification storage track each time a car approaches said retarder track section, means for comparing the outputs of said memory devices for producing an error signal, and means for responding to said error signal for changing the output of said first mentioned memory device to reduce said error signal to zero.

6. In a railroad car classification system including a group retarder track section and a storage track section, the combination of means for supplying a low frequency alternating voltage signal to the input end of the rails of the storage track section for determining the inductive impedance of said track section, said impedance being related to the distance between said input end and the last car on the track, means for producing a D0. track voltage whose magnitude is related to said inductive impedance, a first memory device comprising a first D'.C. amplifier having a first storage capacitor in its output circuit, means for connecting the input of saidamplifier to said D.C. track voltage producing means during a predetermined time interval as a car approaches said retarder to a voltage related to the number of car spaces available along said classification track, a follow-up memory device comprising .ory device to remember the for decreasing the number of a second D.C. amplifier having a second storage capacitor in its output circuit, a source of 30.0. reference voltage adapted to be connected to the input of said second amplifier for charging said second storage capacitor to a reference voltage, a potentiometer having an adjustable tap, said potentiometer being connected to said second capacitor for providing an output voltage at said tap which is a function of said reference voltage and the position of said tap, a comparator comprising a summing operational D.C. amplifier for producing an error signal related to the difference between the voltage stored by said first capacitor and the voltage at said movable contact along said potentiometer, means for responding to said error signal for adjusting the movable contact of said potentiometer to reduce said error signal to zero, and a moving car detector 7 for interrupting said last named means if a car is moving along said classification track.

7. In an automatic speed control system for determining the exit velocity that a car must leave a group retarder to reach'a desired destination upon a classification storage track, the combination of means for generating information proportional to the number of ear spaces available upon said storage track, a car space memory device for storing said information, a follow-up car space memory device, means for correcting said follow-up memnumber of car spaces remembered by said first memory device, means for producing an output that is indicative of a moving car on said track, and means for responding to the moving car output to interrupt the operation of said correcting means.

8.. The combination of claim 7, further including means car spaces remembered by said follow-up memory device for each car that leaves the final retarder.

9.'The combination of claim 7, wherein said information generating means includes means for determining the inductive impedance of the classification track between its input end and the last car on the classification track.

10. In an automatic railroad car classification system the combination of first means for generating information that is proportional to the number of car spaces available upon a classification storage track at any moment, second means for responding to said information during a prede termined time interval prior to the entry of a car upon said storage track to remember the number of car spaces available during said time interval, third means for responding to a change in the information generated by said first means for detecting a moving car on said storage track, and interrupting means for responding to the output of said third means for preventing the number remembered by said second means from being changed during said time interval if a car is moving on said classification track during said interval.

11. The combination of claim means comprises means for supplying an alternating voltage to the rails on said classification track for determining the inductive impedance of said track, and means for producing a DC. voltage whose magnitude is related to said inductive impedance.

12. The combination of claim 11, wherein said third means comprises a DC. amplifier whose input is connected to said DC. voltage producing means by a capacitor, said amplifier having a combination of input and feedback circuits that include resistors and capacitors for generating a smoothed derivative of said DC. voltage.

13. The combination of claim 12, wherein said second means comprises another D.C. amplifier whose input is connected to said capacitor for storing a voltage that is related to said D.C. voltage, a potentiometer having an adjustable tap, means for supplying a DC. reference voltage to said potentiometer, means for comparing the voltage stored by said capacitor with the voltage at the adjustable tap of said potentiometer, and means for changing the position of said tap for reducing a difference between the compared voltages.

10, wherein said first '14xThe combination of'clairn 13, wherein said "comparator comprises a DC. amplifier having an input network for summing output signals from said potentiometer and the capacitor in the output circuit of said other D.C. amplifier, and means including said interrupting means for changing the adjustment of said potentiometer tap for reducing any difference between the inputs of said comparator.

15. In a railroad classification system, the combination of means for generating a DC. voltage that is proportional to the number of car spaces left on a classification track, means for difierentiating said voltage to produce an output in the presence of a moving car upon said track, means for memorizing the number of spaces left on said track in the absence of a moving car upon said track, and means for correcting the number of spaces remembered by said last named means at predetermined moments whenever no car moves on said track.

16. The combination of claim 15, wherein said correcting means is interrupted by the output of said difi'erentiating means in the presence of a moving car upon said track.

17. In a railroad car classification system having a group retarder and at least one storage track spaced from said retarder by a predetermined distance, the combination of a first memory device that includes a first capacitor for storing a first voltage proportional to the actual number of unoccupied car spaces along said storage track, a second memory device that includes a second capacitor for storing a second voltage as a reference, a stepping switch connected across said second capacitor, means for adjusting said stepping switch for obtaining a third voltage that is proportional to the number of unoccupied car spaces that are expected to be available along said track for a car as it approaches said group retarder, means for comparing said first and third voltages to produce an error signal, correcting means for responding to said error signal for operating said stepping switch to reduce said error signal, means for detecting a moving car along said storage track, and means for interrupting the operation of said correcting means if a car is in motion along said storage track.

18. The combination defined by claim 17, further including car count means for operating said stepping switch for changing its output so that it is proportional to one less car space for each car that leaves said retarder regardless of any interruption in the operation of said correcting means.

19. The combination defined by claim 18, wherein said steppingswitch comprises a rotatable switch, a solenoid coil and first and second inputs connected to one end of said coil, an interrupter switch in series with the first one of said coil inputs, means for connecting said correcting means to the first of said coil inputs, and means for connecting said car count means to the second of said coil inputs.

20. The combination as defined by claim 19, further including a relay switch between the output of said comparing means and the input of said correcting means, and means for responding to the output of said moving car detecting means for opening said relay switch if a car is moving along said storage track.

21. In a railway car storage yard including a single track connecting into at least one storage track, a system for indicating the empty car space between the entrance end of each storage track and the nearest car standing in such track, said system comprising, means controlled by each cut of cars traversing said single track for adjusting a first signal for the storage track to which the respective cut is destined, said signal being adjusted proportionately to the number of cars routed to that storage track; means for adjusting a second signal for each storage track proportionately to the empty'car space between the entrance end of such track and the nearest car standing in the track, means for comparing said signals for each storage track and deriving a third signal for that track representative of the difference between the two compared signals, and means controlled by each third signal for readjusting the first signal adjusting means for the corresponding track to bring such first signal substantially into agreement with the second signal for that track.

2 2. In a railway car storage yard including a single track connecting into at least one storage track, a system for indicating the empty car space available in said storage track, said system comprising, means controlled by each cut of cars traversing said single track for adjusting a first signal for the storage track to which the respective cut is destined, said signal being adjusted proportionately to the number of cars routed to that storage track, means for adjusting a second signal for each storage track proportionately to the empty car space between the entrance end of such track and the nearest car in the track, means for comparing said signals for each storage track and deriving a third signal for that track representative of the difference between the two compared signals, a moving car detector associated with each storage track for detecting the movement of a car on that storage track, and means controlled by each third signal and responsive to the output of said moving car detector for readjusting the first signal adjusting means for the corresponding track to bring such first signal substantially into agreement with the second signal when no car is moving upon that track.

23. A system for determining the available storage space on a vehicle storage section having an entrance end comprising, means for developing a signal representative of the distance between said entrance end and the vehicle within said storage section nearest said entrance end, motion detector means for determining whether or not said nearest vehicle is in motion, and means for providing a registration indicative of the available storage space on said storage section in accordance with said developed signal provided that said motion detector means has determined that said nearest vehicle is not in motion.

24. In an automatic railroad car classification system the combination of first means for generating information that is proportional to the number of car spaces available upon a classification storage track at any moment, second means for responding to said information during a predetermined time interval to remember the number of car spaces available during said time interval, third means for responding to a change in the information generated by said first means for detecting a moving car on said storage track, and interrupting means for responding to the output of said third means for preventing the number remembered by said second means from being changed during said time interval if a car is moving on said classification track during said interval.

25. A track fullness system for a storage track in a railway car classification yard, comprising means responsive to each car entering said yard and destined for said storage traok for producing a first signal proportional to the number of cars routed to such track, means for producing a second signal proportional to the distance a car entering said storage track would have to travel to couple with the nearest car in said track, means for comparing said signals and producing a third signal representative of the difference between the two compared signals, and means responsive to said third signal for adjusting said first signal producing means to make said first signal equal said second signal.

26. A track fullness system for a railway car storage track comprising, means responsive to each car appr0aching and destined for said storage track for recording the number of cars occupying the storage track, means controlled by said recording means for deriving a first signal representing said number of cars, means for determining the distance to the nearest car in said storage track, means controlled by said distance determining 15 means for deriving a second signal representing the determined distance, means in said storage track for detecting car movement; means for comparing said signals and producing a third signal representative of the difference between the two compared signals, and means controlled by said third signal and by said detecting means, for correcting said recording means in accordance with said difference, providing said detecting means detects lack of car movement, whereby said first signal deriving means is recontrolled to adjust said first signal to equal said second signal thereby adjusting the track fullness system for unusual length cars and cars that failto travel completely to coupling with the preceding cars in the storage track.

No references cited. 7

ARTHUR L. LA POINT, Primary Examiner. JAMES s. SHANK, LEO QUACKENBUSH, Examiners.

L. J. LEONNING, S. T. KRAWC EWICZ,

Assistant Examiners. 

1. A SYSTEM FOR DETERMINING THE DISTANCE A VEHICLE MUST GO FROM A FIXED POINT ALONG A PREDETERMINED PATH TO A VARIABLE DESTINATION WITHIN A VEHICLE STORAGE SECTION FURTHER ALONG SAID PATH, COMPRISING IN COMBINATION A MEMORY DEVICE FOR STORING INFORMATION RELATING TO THE LENGTH OF THE UNOCCUPIED SPACE WITHIN SAID STORAGE SECTION, MEANS FOR CORRECTING SAID INFORMATION DURING A PREDETERMINED TIME INTERVAL AS A VEHICLE APPROACHES SAID FIXED POINT, MEANS FOR DETECTING MOTION OF ANY VEHICLE WITHIN SAID STORAGE SECTION DURING SAID PREDETERMINED TIME INTERVAL, AND MEANS FOR RESPONDING TO THE DETECTION OF SAID MOTION FOR PRECLUDING CORRECTION OF THE INFORMATION STORED BY SAID MEMORY DEVICE DURING SAID PREDETERMINED TIME INTERVAL. 